1. Field of the Invention
The present invention relates to an automatic focus adjusting apparatus of a camera, and more specifically to an automatic focus adjusting apparatus of a camera in which the camera can be brought into the in-focus state more accurately.
2. Description of the Related Art
Cameras having automatic focus adjusting apparatuses have been available. In a conventional camera having automatic focus adjusting apparatus, if an object is moving, next position of the image plane is estimated in accordance with a function based on amount of defocus in the past, amount of lens drive and amount of defocus at present, and lens is driven to realize in-focus state at the point.
In the conventional camera having the automatic focus adjusting apparatus, correction of the amount of defocus with the object moving has been done by using a linear function. If the speed of movement of the object is slow, well-focused photograph can be taken even if the amount of defocus is corrected by the linear function. However, if the object moves fast, the camera cannot follow the amount of defocus, and accurate correction is impossible.
Now, if the position of image plane of a moving object is to be estimated, the speed of the object must be calculated at first. Conventionally, the speed of the object was calculated by taking a mean value of the speed detected a plurality of times.
However, the speed of the object may change every moment. Accordingly, mean value with weight added to newly detected values provides more accurate information than the simple mean value as calculated in the prior art. However, it takes much time to calculate weighted mean. Consequently, if the object moves fast, there will be a large error due to the delay in calculation.